


to tame a brat

by schoolboy



Category: Shall We Date?: Obey Me!
Genre: Anal Fingering, M/M, Overstimulation, Spanking, shota Mammon
Language: English
Status: Completed
Published: 2020-11-10
Updated: 2020-11-10
Packaged: 2021-03-09 05:14:26
Rating: Explicit
Warnings: No Archive Warnings Apply, Underage
Chapters: 1
Words: 2,874
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27489424
Author URL: https://archiveofourown.org/users/schoolboy/pseuds/schoolboy
Summary: Mammon messed with the wrong witch and got turned into a kid. Lucifer might had too much fun punishing him in his new body.
Relationships: Lucifer/Mammon (Shall We Date?: Obey Me!)
Comments: 8
Kudos: 186





	to tame a brat

**Author's Note:**

> hope yall enjoy mammon's shota tears

\--

  
  


It happens when they're barely done with breakfast, Belphagor half awake and Beelzebub still only on his 5th plate before a heavy chair skids in a hurry. Lucifer looks up and places his fork down.

"And where do you think _you're_ going?"

A tuft of white hair stops in his tracks and Mammon turns to look at him in his fake-casualness. “Business,” Mammon says with a shrug before turning on his heels and continuing to make his way out.

Lucifer sighs as he stands. “And school?”

“Huh? Yeah,” Mammon answers distractedly, already reaching for the door. “I’ll go by myself.”

The door barely creaks opens before it’s slammed closed, Lucifer looming behind Mammon. “What business?”

At Mammon’s silence, Lucifer clicks his tongue. “You can’t skip again.” He grips Mammon’s arm to drag him back to the table. “Satan’s going early so you can leave with him later.”

"No," Mammon starts slowly, quickening his speech once his panic starts to settle in. "No, no, no. I have something _important_ to go to and ya ain't stopping me."

Lucifer could force the answer out of him, but he hasn’t gotten much sleep yesterday and instead settles on staring Mammon down to silently threaten the answer out of him. But Mammon isn’t even looking at him, too busy making a futile attempt to free his arm.

“Solomon mentioned something about a witch yesterday,” Asmodeus chimes in helpfully.

That’s enough explanation needed. 

"Ya don't understand!" Mammon cries out, "I have to meet her or else--"

Lucifer bodily turns Mammon around to face him. "Does the witch really scare you more than _I_ do, Mammon?"

"Luci, you're a fuckin' nightmare," Mammon says seriously. "But the witch is _really_ serious this time I swear, I just need," he pauses to check his phone and from the way his face falls actually makes Lucifer let him go in worry.

"Fuck," Mammon curses.

Then it's as if Mammon is engulfed in some type of magic. Dark smoke swirls all around the younger demon, sparks popping until his brother is no longer visible with a strong force holding him in. Strong enough for Lucifer to take a step back in surprise. 

The smoke clears up soon after and the whole table is now quiet, waiting with bated breath for what has become of their brother. Asmodeus gasps for the dramatic effect when they could only see a lump underneath what Mammon was wearing.

White hair peeks out of the jacket. Next, a head that is too small, with a pair of familiar blue eyes seemingly too big in comparison with his face. The jacket then falls off a narrow shoulder and the tan skin underneath is unmistakable. And when he finally makes all of his way out, there he was, in all his glory: Mammon--or, half of a Mammon. 

Strangely, no one freaks out. 

"Didn't think you could get any smaller," comments Beel offhandedly, tone too genuine for it to be an insult. 

The ends of Levi’s lips curl into a smile. "We can keep him like this forever, right?" 

Maybe it’s because it was Mammon, but Lucifer is glad everyone’s being calm about the situation. Less headache for him. This morning is going better than he thought.

“It was already too late anyway,” Satan convinces Mammon after a minute of him yelling, voice boyish with a higher pitch. “Might as well live with it for a day and see if you’ll go back to normal by yourself.” 

And with that they continued eating with a huffy Mammon, now barely able to see the food on the table. 

Sure, Levi had taken off with Mammon once, exclaiming that he needs to measure Mammon's height just to see if he's Ruri-chan sized now. But he was immediately restrained by Beel as per Lucifer's order, and Satan asks, more amused than curious, "Even if he was the perfect height, what were you going to do with him?"

So, the morning went smoothly.

  
  


Mammon as a kid is, well, just as annoying as he was grown up. This much was already expected. But people were definitely more lenient on him. In fact, Mammon soon realises this and starts purposely messing with people even _more_. 

He didn’t get to have fun for long before his brothers has had enough of him. Especially now that Asmodeus has taken a knack in making Mammon cry, boy tears forming easier than usual even if he tries his best to stop it. It’s rather cute so Lucifer doesn’t chastise Asmodeus for it.

Lucifer does wonder if Mammon’s mental age has decreased along with his physique, but it’s hard to tell when he acts like a child on a daily basis.

So as to not let him attract more attention, Mammon was excused from going to school for today. It should be worrying, leaving him to his own devices. Mostly for their belongings rather than Mammon’s wellbeing, of course. But Lucifer supposes the younger could be left to sulk for a few hours. His younger brothers have started to tease him a little too hard.

Of course, Mammon makes him regret that later. Much later when it was found out that something of the Demon King’s property went missing under Lucifer’s care.

“ _Mammon_ ,” Lucifer says in warning once he finally finds his brother after much difficulty. It took him saying ‘please’ to Satan for the younger demon to smugly inform him Mammon was hiding in his room. So, a lot of pride was risked.

Lucifer holds Mammon up by the scruff of his collar when he finally catches the younger demon, holding him up as if he was a kitten and meets the defiant blue eyes.

"Let me go!" A short leg tries to kick him. "It wasn't me!"

"It's not good to lie, young man."

"Stop trying to act like my dad."

"But you did call me--"

" _Shut up!_ "

Lucifer purses his lips at the tone. But still, it's rather unfair of him to accuse Mammon so fast. So, he asks, “Did you or did you not steal it?”

“Listen,” Mammon says. “It’s really not my fault you left it somewhere easy to find,” Mammon tries to convince him. 

Lucifer stares at him, unimpressed, and starts making his way to his bedroom while Mammon complains for the whole way there. At one point, Mammon admits to where he hid it and tells Lucifer to let him go. Still, swiftly locking the door to his room, Lucifer then throws Mammon onto the bed.

"Hey! Careful with a kid's body!"

"Don't worry.” Lucifer pinches the finger of his glove and pulls it off his right hand. “I'll give you a punishment that's suited for a _child_."

“ _You can’t_.” Mammon scrambles to stand in front of the bed as if to prove a point. Lucifer wonders why he likes making things so hard for himself. “It’s not like I _sold_ it.”

“You would have if I didn’t find you earlier.”

Mammon crosses his arms in a show of anger as he tries to give Lucifer a glare. But it fails once his eyes start to well up from frustration. He blinks once, trying to get rid of the tears but it gets his lashes wet instead and Lucifer sighs. Too cute. Lucifer can't do _anything_ to Mammon when he's like this.

He looks like a doll. 

If it weren't for the fact they have to keep this curse a secret, Lucifer would actually let Mammon take up a few modelling offers with this body. But his need to show Mammon off will have to wait. After all, no matter his size, punishment should be given when due. 

So, Lucifer walks past Mammon and sits on the edge of the bed, resting his hands on his lap as a show of patience. “Mammon,” Lucifer says calmly. “Pants off.”

At this point, even Mammon should realise it's futile to fight back. Naked from the waist down and bent over on Lucifer’s lap like an actual child, he fists his small hands into the sheets, bracing himself for the pain to come. Maybe his mental age didn’t get regressed as well, after all. If so, then this punishment must be more embarrassing than usual. 

Lucifer trails his finger down the spine, pleased from the way the small body shudders underneath. His finger then reaches the plump little butt, just slightly paler compared to the rest of his body. 

It was a good decision to not use any of Lucifer's regular torture devices on Mammon right now because even a single hand he's resting on Mammon's back looks too large in comparison. Lucifer slides his right palm down and realises he has no idea how many hits are appropriate for his brother at this size.

“Fifty,” Lucifer says after a while. They’ve done it enough times for Mammon to understand and he feels Mammon slumping in defeat even if it is a much lower count than usual.

"Be good," is the only warning Lucifer gives before he pulls his hand back.

At the first hit, Mammon jumps more from surprise rather than pain. “One,” Mammon bites out. 

Lucifer hits him harder just from the bratty tone.

" _Fuck_ ," Mammon curses under his breath. “Two,” he quickly adds.

Lucifer continues spanking him, putting more force after each one until he sees the red slowly bloom underneath his palm. His left hand holds Mammon still from shifting and unconsciously trying to move away.

" _Ngh_ , t-ten. _Luci_ ,” Mammon whines. “Slow down.”

Lucifer shushes him.

Lucifer switches from hard to soft smacks, alternating between each cheek and pauses long enough for Mammon to hiss out each number. 

Maybe long enough that Mammon finds time to say something else. “Wa-- _ah_ , wait.” 

It’s a bit too early for a break, but Lucifer rests his palms on a tender cheek, thumbing the soft flesh until Mammon gasps. Then Lucifer lifts his right hand again, and brings his palm down, this time hitting near the top of Mammon’s thighs.

The sharp sound was satisfying. So was the high-pitched cry Mammon had let out response. He takes a big hiccuped breath to form a shaky, “Twenty.”

Maybe he’s getting too much, or maybe because Lucifer keeps hitting him near the top of his thighs where it's most sensitive, but the noises Mammon makes are much louder now. Counts barely heard between his whimpers.

The tan skin is flushed into a lovely colour. They're halfway done, and Lucifer decides he should let Mammon rest while Lucifer squeezes the supple flesh, noting how easily it fits into the palm of his hands.

Mammon lets out a small moan at the feeling, butt probably stinging. So Lucifer moves his hand down, feeling at how soft Mammon's thighs have become. It's delicate, almost. As if Lucifer could break him with just a hand if he so much grips too hard.

But it wasn't like Mammon was originally filled with hard muscles. His body was lean, working out just enough to keep his body fit for modelling. But now he’s soft all over. It's proven how Lucifer barely needed half as much force to stop Mammon from running his mouth.

The break makes Lucifer forget himself for a moment, because the moment he brings his palm down again, the sound of slap between skins is loud and he hears a small sob from the small body. Lucifer pauses, about to turn Mammon over before he feels it. The little prick poking into his thigh.

Though he could guess, Lucifer still slides a hand in between Mammon's thighs, pressing his thumb at Mammon’s taint and cops a feel of his hardened cock. Mammon tries to push himself away but Lucifer easily pins him down. 

"Seems like you enjoyed that a little _too_ much." Lucifer shakes his head with a sigh as if disappointed. But his interest is obvious from how he won’t stop teasing the small erection until Mammon’s letting out these cute gasps. Lucifer almost regrets not touching him earlier. "Even in your child form your body is still lewd."

"It's your fault," Mammon whines, voice muffled from the way he hides his red face into his folded arms. “You made me like this.” Lucifer can hear the pout in Mammon’s voice and he couldn’t help a soft smile from forming.

"Then should I take responsibility?" Lucifer teases the rim under his thumb and feels the way the smaller body pushes into his hand, silently begging for it. Always quick when it comes to rewards despite being nothing but a brat.

Lucifer smacks him lightly once. "Stay still." 

It’s a stretch to get the lube, but Lucifer manages to reach the bedside table with a boy on his lap. Lucifer dribbles the lube on his fingers, quickly warming it up before teasing Mammon’s rim again.

He hears how Mammon lets out a shaky exhale, and whines deep in his throat once Lucifer pushes a finger in. Even two would seem like a stretch for his small body, but Mammon is taking his finger so well, greedy in the way he would rock back and whine for more. So Lucifer pushes another finger into his brother, little boy hole stretched prettily around the long digits. 

The length of his erection presses against the side of Lucifer's thigh when Mammon starts rutting his cock impatiently. Mouth slack open with little moans as he grinds and moves by himself.

Clicking his tongue in disapproval, Lucifer brings his left palm down in warning. Mammon lets out a pained yelp and stays still long enough for Lucifer to start fucking his fingers into him again, curling into the right places.

Mammon moans, loud and too pleased with himself. Almost forgetting that they're in the middle of punishment. So Lucifer brings his palm down, hard as a reminder.

"W-Wait, _ah!_ " Mammon almost squirms off Lucifer's thighs, toes curled from pleasure. 

Lucifer fucks his fingers into Mammon while spanking him in quick succession. The little demon only manages pained ‘ _ah_ ’s while his hole tightens sweetly. All small and sensitive, can’t even decide on moving away or rocking back onto Lucifer’s fingers. Can’t decide if it hurts or feels good.

" _Luci_ ," Mammon whines his name brokenly, telltale of his orgasm quickly nearing. Mammon's body goes bow tight as he keens out his orgasm, little cock rubbing deliciously against Lucifer's thigh, cum staining the fabric even more. Drooly and leaking, making a mess on Lucifer and his bed.

"St-- _ah_ , n-no," Mammon cries out. Mammon's legs kick out under him as he tries to twist his body away but he's easily pinned down from Lucifer's hand splayed across his back. Lucifer doesn’t stop fucking his fingers inside Mammon, prodding at his prostate until he’s near screaming. "No, _can’t_ \--"

It’s too soon when Mammon comes again. Cock barely hard and dry orgasming until he’s crying from oversensitivity. 

He's shaking from his orgasm, whimpering at the feeling of Lucifer’s fingers leaving him empty around nothing. Mammon jumps once Lucifer brings his hand down again, feels the smack across his entire body then sobs, remembering his punishment isn't over. 

It’s definitely worse after his orgasm. His whole body gets too sensitive and the smacks on his butt should probably sting in a way it _burns_. Mammon's butt is a _pretty_ red, and the little demon couldn't stop himself from shaking even if he tried.

"Hurts-- _ah!_ " Mammon cries harder at another smack, knowing Lucifer won't stop until it's over. " _Luci_ \--"

There's barely any hits left. Lucifer lays down the rest quickly, not easing down despite being close to finishing. He needs to make sure Mammon learns his lesson. Though he does have a sobbing boy on his lap, wailing his name louder after each spank. Lucifer can go easy on him for not counting. 

The last one is more like a pat, just a quiet way to tell Mammon good job. Took his punishment with much tears and whinings, but he did well anyway. But Mammon's too gone to even realise it.

He lifts the younger demon easily and gently lays him down on the bed, careful to turn him slightly to the side. Mammon's small body quakes from his sobs. He's rubbing his wet eyes with small hands, trying to control his crying. 

"I'm sor--" _hic!_ "I'm sorry," Mammon apologises shakily. 

"It's okay, you're fine now." Lucifer takes a hold of his small wrists and pulls his hands away from his face, finally seeing the mess of his little demon. Cheeks wet, nose red and running, and face all flushed to his neck, looking so delicious Lucifer could eat him whole. 

He feels almost feral looking at Mammon like this. So defenceless, so vulnerable. Only able to rely on his mercy alone. Doesn’t even realise how hard he’s gripping onto Mammon’s wrists until he hears a hesitant, "Luci?" 

Lucifer drags his gaze from Mammon's heaving chest to his sniffling face again. Kissing the hand in his hold, Lucifer says, "Rest up, sweetheart."

He moves a hand to stroke Mammon’s head, heart blooming when he sees how his younger brother melts from the touch. "Don't worry about the curse," murmurs Lucifer. "I'll take care of it."

Mammon hums sleepily. "You always do."

\--

**Author's Note:**

> [twt](https://twitter.com/mobfushi) | [cc](https://curiouscat.me/gofushi)


End file.
